I actually just shot, err, "filmed" in some schools last week. It's a process for sure, and you gotta have a really good reason for being there and generally can't show any kids' faces. I was working with a group doing an assembly. If I was on my own there's no way I would have been there.
@Indiebudget haha yikes! That reminds me, I almost got called in for "stripping cars" about 10-11 years ago too. We were shooting in a field that belonged to a big organization and we had all the permission to get there. I hadn't actually been there yet, I was with one of their security officers getting some doors unlocked that we needed when a frantic guy pulls up. "hey hey there's a bunch of kids stripping cars in the field"... I thought "isn't that where we're supposed to meet?" then it clicked, and I explained it was us haha.